Development of Teeth

Question 1

teeth consist of 3 hard tissues

Answer 1

enamel, dentin, cementum

Question 2

ectoderm gives rise to

Answer 2

ameloblasts that form enamel

Question 3

neural crest cells give rise to

Answer 3

odontoblasts and cementoblasts which form dentin and cementum

Question 4

mesoderm gives rise to

Answer 4

endothelial cells which form the inner lining of blood vessels

Question 5

what occurs during the 6th week of gestation

Answer 5

formation of dental lamina in the upper and lower jaws

Question 6

dental lamina is

Answer 6

a U-shaped thickening of the oral epithelium that follow the curves of the primitive jaws

Question 7

development of teeth follow 3 stages

Answer 7

bud, cap and bell

Question 8

bud stage

Answer 8

by 7th week
-dental lamina gives rise to 10 tooth buds in each jaw that grown into the underlying mesenchyme
-buds develop into deciduous teeth

Question 9

what does each tooth bud consist of

Answer 9

a proliferation of ectoderm and the condensation mesenchyme surrounding it from neural crest cells

Question 10

bud stage permanent teeth tooth buds

Answer 10

the tooth buds for permanent teeth that have deciduous predecessors begin to appear at approximately 10 weeks from deep continuations of the dental lamina that develop lingual to the deciduous tooth buds

Question 11

since ______ _____ have no deciduous predecessors, they develop as ______ _______ of the dental laminae

Answer 11

permanent molars
posterior extensions

Question 12

cap stage

Answer 12

the proliferated ectoderm of the tooth bud induces the formation of a mesenchymal hillock beneath it, called the dental papilla

Question 13

bell stage

Answer 13

the proliferated ectoderm encloses the dental papilla to form a cap like structure called the enamel organ

mesenchyme surrounding the dental papilla and the dental lamina cap condenses to form the dental sac (dental follicle)

Question 14

the enamel organ consists of

Answer 14

an outer cell layer called the outer enamel epithelium
the inner cell layer lining the papilla called the inner enamel epithelium
central core of loosely arranged cells in-between called the enamel reticulum or stellate reticulum

Question 15

odontoblasts

Answer 15

the outermost cells of the dental papilla adjoining inner enamel epithelium differentiate into odontoblasts
cells go on to secrete predentine which then calcifies to become dentin

Question 16

dentin secretion is triggered by

Answer 16

the inner enamel epithelium and begins at the apex of the tooth moving towards the neck

Question 17

what happens to odontoblasts as dentine thickens

Answer 17

they regress to the center of the dental papilla leaving a thin cytoplasmic process (dental process) embedded in the dentin

Question 18

what is the secondary dentine

Answer 18

when the odontoblast layer persists after tooth eruption and forms dentin throughout life

Question 19

what is tertiary dentine

Answer 19

produced in response to stimuli like tooth damage, or by pulp cells or by odontoblasts

Question 20

what forms the pulp of the tooth

Answer 20

the rest of the cells of the dental papilla

Question 21

ameloblasts

Answer 21

differentiated cells of inner enamel epithelium
under the influence of odontoblasts these cells produce long enamel prisms over the dentin

Question 22

what do the long enamel prisms over the dentin do

Answer 22

matures by increasing mineral content, after which the ameloblasts degenerate

Question 23

root of the tooth development

Answer 23

develops after dentine and enamel

at the neck of the tooth the inner and outer enamel epithelia come together to form the epithelial root sheath

the sheath grows into the mesenchyme and initiates root formation

odontoblasts continue to lay down dentine and as the dentine increases, the pulp cavity narrows to form the root canal

Question 24

dental sac derivatives

Answer 24

inner cells differentiate into cementoblasts which produce cement that is deposited over the dentine of the root and meets the enamel at the neck of the tooth

outer cells become active in bone formation as the jaws ossify

the alveolus (tooth socket) held by the periodontal ligament

Question 25

cementum

Answer 25

the bone-like, mineralized connective tissue covering the root of the tooth

Question 26

periodontal ligament

Answer 26

derived from neural crest cells
a specialized vascular connective tissue that surrounds the root of the tooth, attaching it to the alveolar bone

Question 27

eruption

Answer 27

as the root of the tooth grows, its crown gradually erupts through the oral epithelium

Question 28

which arch erupts first

Answer 28

mandibular teeth before maxillary

Question 29

by the end of the _____ year all children usually have ___ deciduous teeth

Answer 29

second
20

Question 30

what can cause delayed eruption

Answer 30

hypopituitarism
hypothyroidism

Question 31

what gets resorbed by osteoclasts

Answer 31

the root of the corresponding deciduous tooth

Question 32

what affects the shape of the face

Answer 32

the development of the paranasal sinuses and the growth of maxilla and mandible to accommodate teeth

Question 33

natal teeth and why

Answer 33

erupted teeth at birth
usually lower incisors
neonatal teeth - 1 or more teeth erupt later in the neonatal period (1-4 weeks of life)
complications like maternal discomfort while breast feeding, laceration of the neonate’s tongue, aspiration of detached tooth
may need to be extracted and spacers required

Question 34

enamel anomalies

Answer 34

enamel hypoplasia: nutritional deficiency, deficiency of Vit A and D during critical period (6-12 weeks), tetracycline therapy, infections like measles

amelogenesis imperfecta: aberrations in enamel formation, inherited ectodermal birth defect, mutational defects of genes - AMELX, ENAM, and MMP20

Question 35

dentinogenesis imperfecta

Answer 35

can be caused by collagen type I mutations
can be associated with osteogenesis imperfecta
can lead to enamel fractures as the dentine is not hard enough to support the enamel

Question 36

agenesis of maxillary permanent teeth

Answer 36

hypodontia: too few teeth
oligodontia: more than 6 teeth absent
anodontia: complete lack of primary and/or secondary teeth

Question 36

supernumerary teeth: hyperdontia

Answer 36

mesioden: commonest supernumerary tooth between maxillary central incisors
may affect development of adjacent teeth
lateral incisor has contribution from medial nasal process and maxillary process. failure of fusion could cause two lateral incisors along with cleft lip

Question 37

taurodont

Answer 37

increased formation of tooth body and pulp cavity with decrease in the length of the root

Question 38

teeth with extra roots present challenges for

Answer 38

root canal therapy and extraction